Pressure-actuated electrical switch



Nov. 30, 1943. E BRANDS OM 2,335,639

PRESSURE-ACTUATED ELECTRICAL SWITCH Filed Feb. 24, 1943 2 Sheets-Sheet l NOV. 30, 1943. BRANDSTROM 2,335,639

PRESSURE-ACTUATED ELECTRICAL SWITCH Filed Feb. 24, 1943 2 Sheets-Sheet 2 Patented Nov. 30, 1943 UNITED STATES PATENT OFFICE PRESSURE-ACTUATED ELECTRICAL SWITCH Application February 24, 1943, Serial No. 476,940

16 Claims.

This invention pertains to electrical switches and more especially to automatic switches responsive, for example, to changes in temperature or in fluid pressure. In particular the invention concerns automatic switches wherein the switch contacts are closed and opened by a fluid pressure motor, for instance a Bourdon tube, Sylphon, or the like.

Automatic switches of this type are frequently employed for controlling the electrical current supplied for driving the actuating motor for damper regulating means in heating or steam generating systems; automatic stokers; valves in fuel supply lines; valves in refrigerating systems or heating units or motor-driven apparatus in chemical processing, etc. For such and many other purposes it is requisite that there be some definite range or difference between the conditions which cause the switch to close and those which cause it to open. For instance, if during a rise in pressure in a given system, the switch be set to close when a predetermined pressure has been attained, the switch should not open again until the pressure has dropped to a point substantially below that at which the switch closed.

Since it is desirable that the switch, as manufactured, be of general utility, and since, even when a switch has been installed in a given situation operating conditions may change, it is very desirable that the switch be adjustable so that it may be set to close the circuit at any desired point in the scale of pressures or temperatures to which it is designed to respond. Moreover, it is desirable that the range between the closing and opening pressures or temperatures also be variable, in other words, that the closing and opening points be independently adjustable.

Among the objects of the present invention are to provide a switch having provision for independently determining the closing and opening points and thereby varying the range; to provide a switch having graduated, easily visible, and readily accessible adjusting elements whereby the upper and lower limits of the switch range may readily be set by the user; and to provide a switch having all of its acting parts mounted upon a rigid support or chassis independent of the enclosing housing or casing, thereby to prevent forces acting upon the casing from injuring the switch mechanism or changing its setting. A further object is to provide a switch mechanism whose parts are so connected to the actuating motor means as to avoid possibility of injury should the movable parts of the switch for any reason be obstructed in their movements when said motor means begins to act.

Other and further objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings, wherein Fig. 1 is a front elevation of a switch mechanism in accordance with the present invention, the transparent front panel being removed;

Fig. 2 is a vertical section substantially on the line 22 of Fig. 1 but showing the transparent cover panel in place;

Fig. 3 is a front elevation of the rear plate of the frame which supports the movement mechanism of the switch device, showing the mercury switch carrier pivotally mounted on this rear plate;

Fig. 4 is a view similar to Fig. 3 but showing the drive lever in position;

Fig. 5 is a diagrammatic front elevation of the rear plate of the frame showing the relative positions of the assembled switch carrier, drive lever and transmitters;

Fig. 6 is a front elevation showing the assembled suspension levers on which the transmitters are mounted;

Fig. 7 is a diagrammatic front elevation, showing the transmitters mounted on the assembled suspension levers;

Fig. 8 is a diagrammatic front elevation of the drive lever, the overtravel lever and the link lever in normal assembled relation;

Fig. 9 is a rear elevation of the parts shown in Fig. 8;

Fig. 10 is an edge elevation of the parts shown in Fig. 8;

Fig. 11 is a detail, front elevation of one of the transmitter suspension levers;

Fig. 12 is a front elevation of one of the switchsetting cams;

Fig. 13 is a side elevation of one of the combined handle and index elements for the switchsetting cam; and

Fig. 14 is a fragmentary vertical section showing one of the cams assembled with its actuating handle.

Referring to the drawings and particularly to Figs. 1 and 2, the instrument is shown as com prising a protective case or housing of any suitable type but here specifically illustrated as of the kind shown in the patent to Graesser et al. No. 2,271,423, dated January 27, 1942. This case may be of any suitable material, for example a moulded plastic, and has the back wall I, the side walls 2 and the removable transparent front panel 3. As illustarted, the case is furnished with an opening 4 at the lower part of its side wall 2 for the reception of the socket member 5, screw threaded at its lower end as shown at 6 for connection to a suitable pressure supply conduit. In addition to the opening 4 the case may, if desired, have an opening 8 in its rear wall to permit the socket to be extended rearwardly instead of downwardly, to fac litate the mounting of the instrument upon a panel so designed that the supply pipe enters from the rear.

The socket 5 comprises the upward extension 9 which contacts the inner surface of the rear wall of the case and which is secured to the case by screws ill.

The socket also comprises the bracket portion l l to which the fixed end l2 of the Bourdon tube I3 is rigidly secured, the tube l3 having the movable tip I4 and constituting a pressure motor for the actuation of the switch mechanism.

The switch mechanism and the actuating parts are carried by a frame comprising the rear plate l5 (Figs. 2 and 3), the front plate l6 (Figs. 1 and 2) and the rigid posts ll (Fig. 2) which unite the front and rear plates and hold them in properly spaced relation, The rear plate (Fig. 3) has suitable openings for the reception of screws l8 (Fig. 2) by means of which the rear plate and the parts carried thereby is attached to the extension 9 of the socket member. In the upper part of the frame there is arranged a rotary staff l9 (Figs. 2 and 4) journaled at its front and rear ends in the plates l6 and i5 respectively, and having fixed thereto, near its rear end, a switchcarrying member 28 (Figs. 2 and 4-). This member (Figs. 3 and 4) is of more or less T-shape, having the transverse upper portion 20* provided with screw-threaded openings for the reception of screws by means of which the switch bracket 22 (Figs. 1 and 2) is secured to the member 20. This switch bracket 22 is of a conventional type used in mercury switches and designed to receive and securely to hold the glass tube 23 which houses the spaced contacts or terminals 24 and 25 and the body 26 of mercury which at times closes the gap between the terminals or contacts and thus completes an electrical circuit. An abutment pin 21 (Figs. 3 and 4) projects forwardly from the switch carrier 28 at a point above the staff [9,. and the lower end of the member 20 is' forked to provide an upwardly directed recess 28 (Fig. 3) preferably having upwardly convergent walls, said recess receiving a staff 29. This staff 29 is journaled at its rear end in an opening 2S! in the plate l5 of the frame and at its forward end in a bushing 29 (Fig. 1) which is fixedly secured in an opening in the front plate [6. The width of the slot or recess 28 is such as to permit the switch-carrying member 20 to swing about its pivotal axis in opposite directions, but the stafi 20 constitutes a stop to limit such swinging movement.

Mounted on the staff 29 is a drive lever 30 (Figs. 4,. 8, 9 and 10) which extends downwardly to a point below the frame and which is provided with a forwardly directed drive pin 3i near its lower end. Associated with this drive lever 30 is an overtravel lever 32 which is pivoted to swing on. the staff 29'and which, at its free end, is provided with a rearwardly directed rigid stop element 33. (Fig. 10). The overtravel lever also carries' an adjustable stop 34 preferably having a screw driver slot in its forward 'end by means of which it may bev turned, the parts being so devised that the cam step will remain in adjusted position after being turned. This cam stop is so disposed that its edge contacts the edge 35 of the drive lever 39, thus limiting movement of the over-travel lever 32 in one direction (the clockwise direction as viewed in Fig. 8). The overtravel lever 32 is provided with a pivot pin 38 (Fig. 9) on which is mounted the link lever 3?. A spring 38 connects the upper end of this link lever to the drive lever 39, tending constantly to turn the link lever 3'! in a clockwise direction (Fig. 9). Such movement of the link lever is limited by its engagement with the stop 33 at the lower end of the overtravel lever 32. The link lever 31 is provided with an elongate slot 39 at its lower end which receives an adjustable pivot pin carried by the lower end of a link id whose opposite end is' pivotally secured to the tip bracket 4| of the Bourdon tube. The arrangement of parts just described is such that if the drive pin 3| at the lower end of the drive lever 35 meets substantial resistance in either direction of movement of the lever 30, continued movement of the tip M of the Bourdon tube will not overstrain or damage the parts. Thus, for example, if, as viewed in Fig. 9, the pin 3i encounter opposition to movement toward the left while the lower end of the link lever 37 continues to move to the left, the lever 31 will engage the stop 33 and will swing the overtravel. lever 32 in a clockwise direction in opposition to the spring 33. On the other hand, if the drive pin 3! meet abnormal resistance in movement to the right, while the lower end of the link lever 31 continues to move to the right, the link. lever 31 will merely swing about its piv- 0t 36', stretching the spring 33 while the cam stop 34,. by engagement with the edge 35 of lever 38, prevents any relative movement of the levers 32 and 30.

Mounted on the bushing 29 which supports the forward end of the stair 29 is a pair of suspension levers EZ and 63 (Fig. 6). A compression spring 44 interposed between these levers tends to swing themin opposite directions. The lower ends of these levers carry rearwardly projecting studs 45 and 46 respectively, on which are pivotally mounted the vertically elongate transmitter levers 41 and 48 respectively (Figs. 5 and 7). At. their upper ends these transmitter levers have substantially vertical surfaces 49 and 53, respectively, which are disposed at diametrically opposite sides of the abutment pin 2?, while at the lowerends the transmitter levers are furnished with. substantially vertical surfaces 5! and 52 which standv at diametrically opposite sides respectively of the drive pin 35'.

Forwardly of the front plate it of the frame is a pair of graduated dials 53 and 5d, the front plate being furnished with index elements 55 to facilitate the setting of the dials. Each of these dials (Fig. 14) is mounted on a shaft 56 to whose forward end is secured a handle 5? (Figs. 13 and 14) preferably shaped to provide a pointer or index fixed relatively to its respective dial. Each shaft 56 passe through an opening in the front plate 16 of the frame. A cam 58 (Figs. 12 and 14) is fixedly secured to each of the shafts 56, the cams being located behind the front plate It of the frame and being so arranged that the edges of the cams engage shoulders 55, respectively, on the. suspension levers 42 and 43. A spring washer B0 interposed between each dial and the front plate l6 of the frame, acts to retain the cam in adjusted position after being turned by operation of its handle 51.

In the operation of the device and assuming that the pressure motor, that is to say, the Bourdon tube, is responding to an increase in pressure, thus causing its tip l4 to move to the right as viewed in Fig. 1, this motion is transmitted through the link 4!), link lever 31 and drive lever 30 to the pin 3|, thus moving the latter to the right and by engagement with the lower end of the transmitter lever 48 swinging the latter about its fulcrum 46 and thus causing its surface 59, by engagement with the abutment pin 21, to tip the switch carrier 20 to the left 50 that the pool of mercury 26 runs down to the left-hand end of the tube 23, thus breaking the circuit between the contacts 24 and 25. The parts will remain in this position until, due to decrease in pressure, the tip l4 of the Bourdon tube moves to the left (Fig. 1) first restoring the pin 3| to its original position and then, as the tip l4 of the Bourdon tube continues to move to the left, causing the pin 3|, by engagement Withthe surface 5! of the transmitter 41, to swing the latter about its fulcrum 45 and thereby bring it surface 49 into engagement with the abutment pin 21, thus tipping the switch carrier 20 to the right until the pool of mercury 26 engages and closes the gap between the contacts 24 and 25, thus closing the circuit.

Since the two transmitter levers 41' and 48 are independently supported by the suspension levers 42 and 43, and since the latter are independently the position of the other, thus independently determining the distances between each surface 5% or 52, respectively, and the drive pin 3!. It is thus readily possible, by setting the dials 53 and 54, so initially to et the surfaces 5! and 52, that the switch carrier will be swung to break the circuit when the tip M of the Bourdon tube has moved to the right to a predetermined position in response to increase in pressure, and likewise to set the parts so that the switch carrier will be swung to close the circuit when the tip M of the tube has reached a predetermined position in its travel in the opposite direction. It is thus possible to determine the range and differential of the instrument in a very simple manner, so that the pressure points at which th circuit will be opened and closed may be selected as desired and without reference one to the other.

While one desirable embodiment of the invention has been illustrated by way of example, it is to be understood that the invention is not nee essarily limited to this precise arrangement, but is to be regarded as broadly inclusive of all equivalent constructions falling within the terms of the claims.

I claim:

1. A switch mechanism of the class described having spaced electrical contacts and movable circuit-closing means for closing the gap between them, motor means for moving the circuitclosing means to and from gap-closing position, and connections for transmitting motion from the motor means to the circuit-closin means, said connections comprising a single drive element which is movable in either of opposite directions along a predetermined path by the motor, a pair of movable rigid transmitters disposed respectively at opposite sides of the drive element, means operative independently to vary the initial distances between the respective transmitters and the drive element, and an abutment which moves with the circuit-closing means and which is interposed between the transmitters, the transmitters being operative respectively, when actuated by the drive element, to move said abutment together with the circuit-closing means in opposite directions.

2. A switch mechanism of the class described having spaced electrical contacts and movable circuit-closing means for closing the gap between them, motor means for moving the circuit-closing means to and from gap-closing position, and connections for transmitting motion from the motor means to the circuit-closing means, said connections comprising a single drive element supported to move in an arcuate path and movable in either direction along said path by the motor means, a pair of rigid movable transmitters disposed respectively at opposite sides of the drive element, movable supports for the respective transmitters, said supports being independently movable along predetermined different paths and means operative independently to shift said supports thereby to vary the initial distance between the respective transmitters and the drive element, the transmitters being operative respectively, when actuated by the drive element, to move the circuitclosing means in opposite directions.

3. A switch mechanism of the class described having spaced electrical contacts and movable circuit-closing means for closing the gap between them, motor means for moving the circuit-closing means to and from gap-closing position, and connections for transmitting motion from the motor means to the circuit-closing means, comprising a drive element projecting from a supporting lever pivoted to swing about a horizontal axis, means connecting said supporting lever to the motor means whereby the latter may move the supporting lever in either of opposite directions, a pair of movable transmitters disposed respectively at opposite sides of the drive element, pivotal supports for the transmitters, said pivotal supports being movable toward and away from each other thereby to vary the initial distance between the transmitters and the drive element, spring means tending to move said pivotal supports in opposite directions, and adjustable stop means for limiting such movement of the pivotal supports.

4. A switch mechanism of the class described having spaced electrical con acts movable circuit-closing means for closing the gap between them, motor means for moving the circuit-closing means to and from gap-closing position, and connections fOr transmitting motion from the motor means to the circuit-closing means, said connections comprising a drive element supported to move in either of opposite directions, connections between said drive element and the motor whereby the latter may move the drive element in opposite directions, a pair of movable transmitters disposed respectively at opposite sides of the drive element, supporting pivots for the transmitters about which the latter respectively may rock, said supporting pivots being movable toward and from each other thereby to vary the initial distance between the transmitters and the drive element, spring means tending to move said supporting pivots in opposite directions, cam means for limiting such movement of the supporting pivots, a settin device for each cam, and a graduated dial cooperable with each setting device thereby to indicate the position of adjustment of the corresponding cam.

5-. A switch. mechanism of the class described including a switch comprising a pair of spaced electrical contacts and a movable body of. metal for closing the gap between said contacts, the: contacts and gap-closing means beinghoused in a sealed container, a movable carrier for the container, motor means for moving said carrier in opposite directions thereby respectively to close or open the gap between the contacts, and connections for transmitting motion from the motor means to the movable carrier, said connections including a drive element movable in either of opposite directions by the motor, a pair of elongate normally substantially parallel transmitters each having one end arranged for engagement with a part of the carrier, the opposite ends of the transmitters being disposed respectively at opposite sides of the drive element, independently movable supports for the transmitters, and man-- ually actuable means for adjusting said movable supports, the engagement of the drive element with either transmitter causing the switch carrier to move thereby respectively to close or open the gap between the contacts.

6. A switch mechanism of the class described including a switch comprising a pairoi spaced electrical contacts and a movable body of metal for closing the gap between said contacts, the contacts and gap-closin means being housed in a sealed container, a movable carrier for the container, motor means for moving said carrier in opposite directions thereby respectively to close or open the gap between the contacts, and connections for transmitting motion from the motor means to the movable carrier, said connections including a drive element movable in either of opposite directions by the motor, a pair of elongate normally substantially arallel transmitters each having one end arranged for engagement with a part of the carrier, the opposite ends of the transmitters being disposed respectively at opposite sides of the drive element, a pivotal support for each transmitter, the pivotal supports being movable toward and away from each other, spring means urging the pivotal supports away from each other, and independentl adjustable stops for limiting said movement of each support.

7. A switch mechanism of the class described including a switch comprising a pair of spaced electrical contacts and a movable body'of metal for closing the gap between said contacts, the contacts and gap-closing means being housed in a sealed container, a movable carrier for the container, motor means for moving said carrier in opposite directions thereby respectively to close or open the gap between the contacts, and connections for transmitting motion from the motor means to the movable carrier, said connections including a drive element movable in either of opposite directions by the motor, a pair of elongate normally substantially parallel transmitters each having one end arranged for engagement with a part of the carrier, the opposite ends of the transmitters being disposed respectively at opposite sides of the drive element, a pair of suspension arms each carryin a pivot pin adjacent to its free end, each pivot pin respectively forming a fulcrum for one of the transmitters, spring means urging the suspension arms away from each other, and independently adjustable stops operative to limit said movement of the suspension arms.

8. A switch mechanism of the class described including a switch comprising a pair of spaced electrical contacts and a movable body of metal for closing the gap between said contacts, the contacts and gap-closing means being housed in a sealed container, a movable carrier for the container, motor means for moving said carrier in opposite directions thereby respectively to close or open the gap between the contacts, and connections for transmitting motion from the motor means to the movable carrier, said connections including a drive element movable in either of opposite directions by the motor, a pair of elongate normally substantially parallel transmitters each havin one end arranged for engagement with a part of the carrier, the opposite ends of the transmitters being disposed respectively at opposite sides of the drive element, a pair of suspension arms each carrying a pivot pin adjacent to its free end, each pivot pin respectively forming a fulcrum for one of the transmitters, spring means urging the suspension arms away from each other, a rotary cam stop for limiting said motion of each rock arm, a graduated dial coaxial with each cam stop, and means for turning each cam stop including an index element cooperable with the respective dial.

9. A switch mechanism of the class described including a mercury switch and a pivoted carrier for the switch, said carrier being rockable in opposite directions about a horizontal axis thereby to make or break a switch circuit, said carrier having a forked tail portion cooperable with a fixed stop thereby to limit movement of the switch carrier in both directions, said carrier having a forwardly directed abutment element intermediate its pivotal axis and the switch, a pair of independently movable transmitters, said abutment element being disposed between said transmitters, pivotal supports for the transmitters, a drive element interposed between the transmitters, and motor means operative to move the drive element into engagement with one or the other of the transmitters thereby to rock the switch carrier.

10. A switch mechanism of the class described including a mercury switch and a pivoted carrier for the switch, said carrier being rockable in opposite directions about a horizontal axis thereby to make or break a switch circuit, said carrier having a forked tail portion cooperable with a fixed stop thereby to limit movement of the switch carrier in both directions, said carrier having a forwardly directed abutment element intermediate its pivotal axis and the switch, a pair of elongate rigid substantially parallel transmitters each pivotally mounted at a point intermediate its ends so as to swing about a horizontal axis, the upper ends of the transmitters being disposed respectively at opposite sides of the abutment, a drive element interposed between the lower ends of the transmitters, and motor means operative to move the drive element into operative engagement with one or the other of the transmitters thereby to rock the latter to tip the switch carrier.

11. In combination in switch mechanism of the class described, a switch and an oscillatory carrier therefor, motor means for moving the carrier, a rigid abutment projecting from the carrier, two rigid transmitters disposed at opposite sides respectively of the abutment, a drive element interposed between the transmitters, and yieldable connections between the motor means and the drive element operative to permit continued movement of the motor means in either direction after the carrier has reached a normal limit in its arc of oscillation.

12. A switch mechanism of the class described including a mercury switch and a, pivoted carrier for the switch rockable in opposite directions about a horizontal axis thereby to make and break the switch circuit, motor means for moving the carrier in one direction or the other, a rigid abutment projecting from the carrier at a point at the opposite side of the pivotal axis of the carrier from the switch, two rigid elongate pivoted transmitters, one end portion of one transmitter being disposed at one side of the abutment and the corresponding end portion of the other transmitter being disposed at the opposite side of said abutment, a drive element interposed between the opposite end portions of the transmitters, and connections for transmittin motion from the motor means to the drive element, said connections comprising a resiliently yieldable element.

13. In combination in switch mechanism of the class described, a switch and an oscillatory carrier therefor, a Bourdon tube constituting motor means for moving the carrier, a pair of elongate substantially parallel transmitters, the carrier having a part which is interposed between end portions of the transmitters, a drive lever having a drive element interposed between the transmitters near their opposite ends, and yieldable connections between the tip of the Bourdon tube and the drive lever, said connections being operative normally to transmit motion from the tube tip to the drive lever but being so constructed and arranged as to permit relative movement of the tube tip and drive lever in either direction after the drive lever has oscillated through a predetermined arc.

14. In combination in switch mechanism of the class described, a mercury switch and an oscillatory carrier therefor, a Bourdon tube constituting motor means for moving the carrier, a drive lever pivotally supported near its upper end and having a stud projecting from its lower end constituting a drive element, connections between the drive element and the switch carrier for oscillating the latter, an overtravel lever pivotally supported by the drive lever, and a link lever supported by the overtravel lever, the link lever having a slot which receives adjustable pivot means which connects it to a link pivotally attached to the tip of the Bourdon tube, a spring connecting the link lever and the overtravel lever, and stops operative to limit movement of the link and overtravel levers in response to the action of the spring.

15. In combination in switch mechanism of the class described, a mercury switch and an oscillatory carrier therefor, a Bourdon. tube constituting motor means for moving the carrier, a drive lever pivotally supported near its upper end and having a stud projecting from its lower end constituting a drive element, connections between the drive element and the switch carrier for oscillating the latter, an overtravel lever pivotally supported by the drive lever, and a link lever supported by the overtravel lever, the link lever having a slot which receives adjustable pivot means which connects it to a link pivotally connected to the tip of the Bourdon tube, a spring connecting the link lever and the overtravel lever, the parts being so constructed and arranged that the spring tends to resist motion of the link lever in a clockwise direction and to resist motion of the overtravel lever in a counterclockwise direction, and stop means to limit such motion of each lever.

16. A switch mechanism of the class described including a mercury switch and a movable carrier for the switch, motor means for moving the carrier thereby to close or open the switch, and connections for transmitting motion from the motor means to the carrier, said connections comprising a drive element which is movable in each of opposite directions by the motor, a drive lever supporting the drive element, an overtravel lever pivotally connected to the drive lever, a link lever pivoted at a point between its ends to the free end of the overtravel lever, a stop carried by the overtravel lever for limiting movement of the link lever in one direction, a tension spring connecting the link lever to the drive lever and urging the link lever against said stop, an adjustable stop cam carried by the overtravel lever for limiting motion of the overtravel lever relatively to the drive lever in response to the action of the spring, and a link connecting the link lever to the motor means.

FRED BRANDSTROM. 

